PROJECT SUMMARY/ABSTRACT Hispanics/Latinos experience disproportionately high rates of cardiovascular (CVD) and other diseases. Those who engage in high amounts of sedentary time are believed to be at increased risk for chronic diseases, even if they engage in moderate amounts of physical activity. However, 2 individuals with the same amount of sedentary time (e.g., 10 hours per day) can accumulate sedentary time differently, through either short interrupted bouts of sitting or prolonged uninterrupted bouts of sitting. The latter ?sedentary pattern? is believed to be more detrimental to health. However, evidence to support this hypothesis is limited because it has been primarily derived from hip accelerometers, which do not accurately measure sedentary patterns. Thus, a critical next step in this area of research is to identify what new information is learned about sedentary patterns in free-living population cohorts when they are measured more accurately by the activPAL. This observational cohort study will investigate how various sedentary patterns are cross-sectionally (Aim 1a) and prospectively (Aim 2a) associated with CVD risk markers of adiposity, insulin resistance, and blood glucose in 2600 Hispanics/Latinos from 4 regions across the US. Sedentary-risk marker associations will be compared between hip accelerometers (the traditional method) and activPAL (the more accurate method). The role of physical activity and total sedentary time as effect modifiers of the association of sedentary patterns with CVD risk markers will also be investigated (Aims 1&2b) to inform efforts targeting the full spectrum of light, moderate, and vigorous activity. The role of key settings for sedentary time will be explored to inform setting- and individually-tailored efforts and recommendations. These settings will be assessed by Global Positioning Systems and include the home, worksite, neighborhood, and transportation. Study participants will be from the Hispanic Community Healthy Study/Study of Latinos (HCHS/SOL), a multi-site community-based cohort of adults aged 18-74 at Visit 1 (2008-2011) focused on improving Hispanic/Latino health. The study outcome variables will include waist-to-hip ratio, percent body fat, and body mass index (measures of adiposity), HOMA-IR (a measure of insulin resistance) and HbA1c (a measure of blood glucose), which are priorities for disease prevention in Hispanics/Latinos. Multiple novel sedentary pattern variables will be investigated to identify which aspects of sedentary time are most important for health in this population. Rigorous statistical analyses will test each study aim, and gender- and age-group specific findings and recommendations will be provided if warranted. Findings will advance science and measurement by identifying whether and how inferences differ based on the method used to assess sedentary patterns. Findings will inform practice by identifying which specific aspects of sedentary patterns should be targeted to improve risk markers. Improving understanding of the health implications of sedentary patterns has promise for enhancing population health in Hispanics/Latinos and other population groups and complements efforts to increase population physical activity.